1. Field of the Invention
The present invention relates to a storage system and a storage management method, and more particularly to a storage system which manages data in a storage area of a storage device for a long period of time in a computer system using a computer and the storage device.
2. Description of the Related Art
In a computer system in companies or the like, in accordance with the increase in the amount of storage data and the prolonged storage period of data, the capacity of storage media for storing data has also been increased. Further, in order to store data for a long period of time, the life of the storage media needs to be considered. Among data storage media, there is a nonvolatile semiconductor memory as exemplified by a write-frequency limited type memory such as a flash memory. The flash memory has a limitation of write frequency, but is generally said to have a longer life as compared with the disk drive because the flash memory can be operated without power for rotating the drive or the like.
Further, in order to compensate the limitation of write frequency of the flash memory, there is disclosed a technique in Japanese Patent Laid-Open No. 6-124596 (Patent document 1), in which a controller manages the frequency of writing to sectors of the flash memory so as to prevent erasing parts from being concentrated on specific sectors, thereby enabling the life of the flash memory to be prolonged.
There are following problems in such conventional method. As a result of the extension of the life of the storage medium constituted by the flash memory, the life of the storage medium may be longer than that of the controller which controls the storage medium. In this case, it is possible to use the same flash memory in such a manner that the flash memory is removed from the storage device, that is, placed in off-line mode so as to be loaded onto another storage device, or that the controller whose life is expired is replaced by another controller.
However, in the conventional technique, since management information is managed by the controller, when the flash memory is removed and operated by being loaded onto another controller, the write frequency, that is, the life of the flash memory to the writing is not taken over. As a result, the new controller is unable to grasp the use degree of the flash memory.